This is the first article of the series that I have planned to write explaining the Cryptography behind . Blockchain In this article, I will be covering One-Way Functions. To understand the need for one-way functions, let me first help you understand Two-Way functions. Two-Way Functions Let us assume that we have a function f(x)=y. Whenever we give input as “x”, we get an output “y”. Now let us look at the following table: If we observe the above Input and Output values, by close observation we find that output is always the square of the input, i.e y=x*x. Or f(x)=x*x. Now, let us say that the function generates an output as “121”. Since I know the function, I can easily tell that the input would have been “11”. Functions wherein we can determine the input with the help of its output are known as . Two-way functions As much as we have enjoyed cracking this function we should realize that if we incorporate them in the Systems or Application Design, any hacker can crack open the application with a simple . brute force attack This particular of Two-way functions led to the adoption of One-way functions. vulnerability One-Way Functions Let us consider the SHA256 of the following numbers. SHA256(1) = 6B86B273FF34FCE19D6B804EFF5A3F5747ADA4EAA22F1D49C01E52DDB7875B4B SHA256(2) = D4735E3A265E16EEE03F59718B9B5D03019C07D8B6C51F90DA3A666EEC13AB35 SHA256(3) = 4E07408562BEDB8B60CE05C1DECFE3AD16B72230967DE01F640B7E4729B49FCE If you observe the above three outputs, they do not follow a pattern. Thus, there is no way we can identify the input of the function. When these functions are used in applications, it is for a hacker to penetrate into the application. Such functions are known as not an easy task One-Way Functions. The following quote was my motivation to write this article: “Technology is applied science. Science is the study of nature. Mathematics is the language of nature. Philosophy is the root of mathematics. All tightly interrelated.”~Naval Ravikant In the upcoming articles of this series, I will be explaining and how they are incorporated in . Stay tuned for the updates! Thank you for reading my article. Hashing Algorithms Blockchain Design If you have any questions, please feel free to send me an email . You can also contact me via Linkedin . You can also follow me on Twitter . In order to get started with Blockchain read my article published on Hackernoon